Insulated Conductive Strands With Polymer Cores

ABSTRACT

An item may include fabric or other materials formed from intertwined strands of material. The item may include circuitry that produces signals. The strands of material may include non-conductive strands and conductive strands. The non-conductive strands and conductive strands may be close in size. The conductive strands may carry the signals produced by the circuitry. Each conductive strand may have a strand core, a conductive coating on the strand core, and an insulating coating on the conductive coating. The strand cores may be strands formed from polymer. The conductive coating may be formed from metal. The insulating coating may have a relatively thin thickness and may be formed from a polymer.

This application is a continuation of U.S. patent application Ser. No. 15/578, 196, filed Nov. 29, 2017, which is a 371 of international patent application No. PCT/US2016/031646, filed May 10, 2016, which claims priority to provisional patent application No. 62/170,630, filed Jun. 3, 2015, which are hereby incorporated by reference herein in their entireties.

BACKGROUND

This relates generally to items formed from strands of material, and, more particularly, to items formed from strands of material such as insulated conductive strands with dielectric cores.

It may be desirable to form items such a bags, clothing, and other items from intertwined strands of material. For example, woven or knitted fabric or braided strands may be used in forming portions of an item.

In some situations, may be desirable for some or all of a strand of material in an item to be conductive. Conductive strands may be used, for example, to carry signals between circuitry in different portions of an item. Strands such as conductive strands may serve both mechanical functions (e.g., by forming a part of a fabric) and/or electrical functions (e.g., by conveying signals).

Challenges may arise when forming items such as fabric-based items with conductive strands. It is often desirable for conductive strands to exhibit good mechanical properties, such as high strength and flexibility. Because conductive strands may need to carry electrical signals, the resistance of a conductive strand should generally not be too high. Conductive strands should also be compatible with the non-conductive strands in a fabric and should not form undesired short circuits with surrounding structures. If care is not taken, conductive strands in a fabric-based item may be overly fragile, may exhibit poor signal carrying capabilities, may be insufficiently isolated from surrounding structures, or may adversely affect the appearance and feel of the item.

It would therefore be desirable to be able to provide strand-based items that incorporate improved conductive strands.

SUMMARY

An item may include fabric or other materials formed from intertwined strands of material. The item may include circuitry that produces signals. The strands of material may include non-conductive strands and conductive strands. Strands may be intertwined using weaving equipment, knitting equipment, braiding equipment, or other equipment for intertwining strands of material. If desired, the non-conductive strands and conductive strands may be close in size (e.g., to minimize or eliminate perceptible differences in the appearance and feel of the non-conductive and conductive strands).

The conductive strands may carry the signals produced by the circuitry. Each conductive strand may have a strand core, a conductive coating on the strand core, and an insulating coating on the conductive coating. The strand cores may be formed from polymers such as para-aramids and aromatic polyesters (as examples). The conductive coating may be formed from a metal such as silver or other metals. The insulating coating may be a relatively thin insulator such as an insulator with a thickness of less than 5 microns or other suitable thickness. Examples of materials that may be used for forming the insulator include polyvinyl formal, polyester-polyimide, polyamide-polyimide, polyamide, polyimide, polyester, polytetrafluoroethylene, polyurethane, and other polymers.

Polymer strand cores may be formed by extrusion, spinning, or other techniques. Metal coatings for the strand cores may be formed by electrochemical deposition or other metal deposition techniques. Insulating coatings may be formed by applying liquid polymer in a thin layer to the exterior of a strand that has been coated with metal and by applying heat or otherwise curing the liquid polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative strand-based item in accordance with an embodiment.

FIG. 2 is a diagram of a portion of a fabric with conductive strands in accordance with an embodiment.

FIG. 3 is a diagram of illustrative equipment of the type that may be used in forming insulated conductive strands with dielectric cores and strand-based items that include insulated conductive strands with dielectric cores in accordance with an embodiment.

FIG. 4 is a side view of illustrative equipment for forming a dielectric core and coating the core with a conductive material such as metal for a strand in accordance with an embodiment.

FIG. 5 is a side view of illustrative equipment for adding an insulating coating to a conductive strand in accordance with an embodiment.

FIG. 6 is a cross-sectional view of a dielectric strand core in accordance with an embodiment.

FIG. 7 is a cross-sectional view of a strand having a dielectric core and a conductive coating layer in accordance with an embodiment.

FIG. 8 is a cross-sectional view of a strand having a dielectric core, a conductive coating, and an insulating coating in accordance with an embodiment.

FIG. 9 is a flow chart of illustrative steps involved in forming conductive strands with dielectric cores and insulating coatings and in forming strand-based items from such strands in accordance with an embodiment.

DETAILED DESCRIPTION

Strands of material may be incorporated into strand-based items such as strand-based item 10 of FIG. 1. Item 10 may be an electronic device or an accessory for an electronic device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user's head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which fabric-based item 10 is mounted in a kiosk, in an automobile, airplane, or other vehicle, other electronic equipment, or equipment that implements the functionality of two or more of these devices. If desired, item 10 may be a removable external case for electronic equipment, may be a strap, may be a wrist band or head band, may be a removable cover for a device, may be a case or bag that has straps or that has other structures to receive and carry electronic equipment and other items, may be a necklace or arm band, may be a wallet, sleeve, pocket, or other structure into which electronic equipment or other items may be inserted, may be part of a chair, sofa, or other seating (e.g., cushions or other seating structures), may be part of an item of clothing or other wearable item (e.g., a hat, belt, wrist band, headband, etc.), or may be any other suitable strand-based item.

Strands in strand-based item 10 may form all or part of a housing wall for an electronic device, may form internal structures in an electronic device, or may form other strand-based structures. Strand-based item 10 may be soft (e.g., item 10 may have a fabric surface that yields to a light touch), may have a rigid feel (e.g., the surface of item 10 may be formed from a stiff fabric), may be coarse, may be smooth, may have ribs or other patterned textures, and/or may be formed as part of a device that has portions formed from non-fabric structures of plastic, metal, glass, crystalline materials, ceramics, or other materials.

Item 10 may include intertwined strands 12. The strands may be intertwined using strand intertwining equipment such as weaving equipment, knitting equipment, braiding equipment, or equipment that intertwines strands by entangling the strands with each other in other ways (e.g., to form felt). Intertwined strands 12 may, for example, form woven or knitted fabric or other fabric (i.e., item 10 may be a fabric-based item), a braided cord, etc.

Strands 12 may be single-filament strands or may be threads, yarns, or other strands that have been formed by intertwining multiple filaments of material together. Strands 12 may be formed from polymer, metal, glass, graphite, ceramic, natural fibers such as cotton, bamboo, wool, or other organic and/or inorganic materials and combinations of these materials. Strands 12 may be insulating or conductive.

Conductive coatings such as metal coatings may be formed on non-conductive strands (e.g., plastic cores) to make them conductive and strands such as these may be coated with insulation or left bare. Reflective coatings such as metal coatings may be applied to strands 12 to make them reflective. Strands 12 may also be formed from single-filament metal wire, multifilament wire, or combinations of different materials.

Strands 12 may be conductive along their entire length or may have conductive segments (e.g., metal portions that are exposed by locally removing insulation or that are formed by adding a conductive layer to a portion of a non-conductive strand.). Threads and other multifilament yarns that have been formed from intertwined filaments may contain mixtures of conductive fibers and insulating fibers (e.g., metal strands or metal coated strands with or without exterior insulating layers may be used in combination with solid plastic fibers or natural fibers that are insulating).

Item 10 may include additional mechanical structures 14 such as polymer binder to hold strands 12 together, support structures such as frame members, housing structures (e.g., an electronic device housing), and other mechanical structures.

Circuitry 16 may be included in item 10. Circuitry 16 may include components that are coupled to strands 12, components that are housed within an enclosure formed by strands 12, components that are attached to strands 12 using welds, solder joints, adhesive bonds (e.g., conductive adhesive bonds), crimped connections, or other electrical and/or mechanical bonds. Circuitry 16 may include metal structures for carrying current, integrated circuits, discrete electrical components such as resistors, capacitors, and inductors, switches, connectors, light-emitting components such as light-emitting diodes, audio components such as microphones and speakers, vibrators, solenoids, piezoelectric devices, and other electromechanical devices, connectors, microelectromechanical systems (MEMs) devices, pressure sensors, light detectors, proximity sensors, force sensors, moisture sensors, temperature sensors, accelerometers, gyroscopes, compasses, magnetic sensors, touch sensors, and other sensors, components that form displays, touch sensors arrays (e.g., arrays of capacitive touch sensor electrodes to form a touch sensor that detects touch events in two dimensions), and other input-output devices. Circuitry 16 may also include control circuitry such as non-volatile and volatile memory, microprocessors, application-specific integrated circuits, system-on-chip devices, baseband processors, wired and wireless communications circuitry, and other integrated circuits.

Item 10 may interact with electronic equipment or other additional items 18. Items 18 may be attached to item 10 or item 10 and item 18 may be separate items that are configured to operate with each other (e.g., when one item is a case and the other is a device that fits within the case, etc.). Circuitry 16 may include antennas and other structures for supporting wireless communications with item 18. Item 18 may also interact with strand-based item 10 using a wired communications link or other connection that allows information to be exchanged.

In some situations, item 18 may be an electronic device such as a cellular telephone, computer, or other portable electronic device and strand-based item 10 may form a case or other structure that receives the electronic device in a pocket, an interior cavity, or other portion of item 10. In other situations, item 18 may be a wrist-watch device or other electronic device and item 10 may be a strap or other strand-based item that is attached to item 18. In still other situations, item 10 may be an electronic device, strands 12 may be used in forming the electronic device, and additional items 18 may include accessories or other devices that interact with item 10.

If desired, magnets and other structures in items 10 and/or 18 may allow items 10 and 18 to interact wirelessly. One item may, for example, include a magnet that produces a magnetic field and the other item may include a magnetic switch or magnetic sensor that responds in the presence of the magnetic field. Items 10 and 18 may also interact with themselves or each other using pressure-sensitive switches, pressure sensors, force sensors, proximity sensors, light-based sensors, interlocking electrical connectors, etc.

The strands that make up item 10 may be intertwined using any suitable strand intertwining equipment. For example, strands 12 may be woven together to form a fabric. The fabric may have a plain weave, a satin weave, a twill weave, or variations of these weaves, may be a three-dimensional woven fabric, or may be other suitable woven fabric. If desired, the strands that make up item 10 may be intertwined using knitting equipment, braiding equipment, or other strand intertwining equipment. Item 10 may also incorporate more than one type of fabric or intertwined strand-based material (e.g., item 10 may include both woven and knitted portions).

The strands that make up item 10 may be intertwined to form a fabric such as illustrative fabric 20 of FIG. 2. Fabric 20 may include strands 12. Strands 12 may be formed from conductive and/or insulating materials. As an example, fabric may be formed from insulating strands 28 interspersed with conductive strands 22. In the illustrative configuration of FIG. 2, a first conductive strand 22 extends vertically and electrically connects node A with junction 24 and a second conductive strand 22 extends horizontally (i.e., perpendicular to the first conductive strand) and electrically connects node B with junction 24. At the intersection of the first and second conductive strands at junction 24, the first and second strands may be electrically connected using mechanical contact, solder, welds, conductive adhesive, a crimped metal connection or other metal connector, or other electrical connection structure. Using this type of technique, desired signal paths such as illustrative signal path 26 between nodes A and B may be formed within fabric 20 (e.g., to form signal busses, to form electrodes or other parts of sensors, to form other conductive structures, etc.).

Conductive strands such as conductive strands 22 in illustrative fabric 20 for item 10 may be formed from one or more layered materials. For example, conductive strand 22 may have a core (e.g., an elongated member such as a monofilament), a conductive inner coating, and an outer insulating coating.

The different portions of the conductive strand may be formed from different materials or, if desired, two or more of the portions of the conductive strand may be formed from the same material. As an example, a conductive strand may have a core and an outer coating that are formed from a common dielectric and that are separated by an intermediate layer formed from a conductive material. Configurations may also be used in which a conductive strand has a core formed from a first dielectric and an outer layer formed from a second dielectric and in which the first and second dielectrics are separated from each other by an intervening conductive layer such as a metal layer.

In some configurations, conductive strand 22 may contain polymer. For example, conductive strand 22 may contain a polymer core to provide strand 22 with strength and flexibility. Polymer may also be used in forming insulating outer coating layers. Examples of polymers that may be used in forming a core and/or an outer insulating coating for conductive strand 22 include polyamide (nylon—e.g., nylon6, nylon6,6, nylon 11), aromatic polyamide (i.e., para-aramids such as Kevlar® or other aramids), polyimide, polyester, polyolefin, acrylic, aromatic polyesters such as Vectran®, polyethylene, extruded cellulosic polymers such as rayon and Tencel®, polyvinyl formal, polyester-polyimide, polyamide-polyimide, polytetrafluoroethylene, and polyurethane. Other polymers or mixtures of these polymers may be used, if desired. Inorganic materials may also be used in forming dielectric strand cores and insulating layers. Illustrative configurations in which these strand structures are formed from polymers are sometimes described herein as an example.

The polymer materials of strand 22 may be formed from conductive organic material, from insulating polymeric materials (e.g., materials to form a dielectric core and/or outer coating), from polymer that includes conductive filler such as particles of metal, particles of carbon nanotube material, graphene particles, fibrous carbon material, or other conductive particles. Conductive filler may be incorporated into the polymer in a concentration that renders a portion of strand 22 conductive or may be incorporated into the polymer in a lower concentration (e.g., to promote adhesion or otherwise enhance compatibility with other portions of strand 22 without necessarily increasing the conductivity of the polymer to a level that allows the material to serve as a conductive signal path in fabric 20).

In some situations, monofilaments may be formed of metal or polymer (i.e., polymer with conductive filler or without conductive filter). These monofilaments may be intertwined to form strands 22 or portions of strands 22. In general, strands 22 may have one or more materials, two or more materials, three or more materials, four or more materials, or five or more materials. The structures of strands 22 may incorporate conductive materials such as metal, insulating materials such as polymer, conductive organic materials such as conductive polymer, polymer filled with metal particles and other conductive filler, other materials, and/or combinations of these materials.

FIG. 3 is a diagram showing different types of equipment 60 that may be used in processing strands 12 (e.g., non-conductive strands 28 and conductive strands 22) and/or that may be used in processing strand-based item 10. As shown in FIG. 3, equipment 60 may include strand core formation equipment 68. Equipment 68 may include, for example, equipment for extruding and/or otherwise forming polymer cores for strands 12. Conductive coating application tool 62 may be used to apply one or more conductive coatings. For example, tool 62 may be used to apply a metal coating to a polymer strand core to form a conductive strand 22. Dielectric coating application tool 66 may be used to apply a polymer layer or other insulating coating. For example, tool 66 may be used to apply a thin polymer coating to the exposed metal coating on a polymer strand core, thereby forming an insulated conductive strand 22.

Equipment 64 may be used in processing strands 12. Equipment 64 may include a heat source (e.g., a flame, a heated metal structure or other heated structure, a lamp that produces heat, an oven, etc.). Equipment 64 may also include a laser, light-emitting diode, or other light source (e.g., an infrared laser or infrared light-emitting diode, a visible laser or visible light-emitting diode, and/or an ultraviolet laser or light-emitting diode). By applying heat or light or other energy to strands 12 or by using equipment 64 to mechanically or chemically remove material from strands 12, coatings can be selectively removed, liquid polymers and other coating materials may be cured, the texture of strand 12 may be altered, or other strand modifications can be made.

Equipment 64 may be used in attaching electrical components such as electrical components in circuitry 16 of FIG. 1 to strands such as conductive strands 22. For example, equipment 64 may be used to attach electrical components to strands 22 using solder joints, crimped metal connections, welds, conductive adhesive, or other conductive attachment structures. The electrical components that are attached to strands in this way may include light-emitting components, integrated circuits, light-emitting diodes, light-emitting diodes that are packaged with transistor-based circuitry such as communications circuitry and/or light-emitting diode driver circuitry that allows each component to operate as a pixel in a display, discrete components such as resistors, capacitors, and inductors, audio components such as microphones and/or speakers, sensors such as touch sensors (with or without co-located touch sensor processing circuitry), accelerometers, temperature sensors, force sensors, microelectromechanical systems (MEMS) devices, transducers, solenoids, electromagnets, pressure sensors, light-sensors, proximity sensors, buttons, switches, two-terminal devices, three-terminal devices, devices with four or more contacts, etc. Electrical connections for attaching electrical components to strands 12 using equipment 64 may be formed using solder, conductive adhesive, welds, molded package parts, mechanical fasteners, wrapped strand connections, press-fit connections, crimped connections (e.g., bend metal prong connections), and other mechanical connections, portions of liquid coatings (e.g., metallic paint, conductive adhesive, etc.) that are selectively applied to strands 12 using equipment 100, or using any other suitable arrangement for forming an electrical short between conductive structures.

Strand intertwining equipment 70 (e.g., weaving equipment, knitting equipment, braiding equipment, or other strand intertwining equipment) may be used in intertwining strands 12 to form fabric and other structures for strand-based item 10. Equipment 60 may be used to process strands 12 before, during, or after processing of strands 12 with equipment 70 to form item 10.

FIG. 4 is a diagram of illustrative equipment for forming a polymer strand core that is coated with a metal coating. As shown in FIG. 4, polymer strand core 80 may be produced by polymer strand formation tool 68 (e.g., an extrusion tool, a polymer fiber spinning tool, etc.). Tool 68 may dispense core 80 in direction 84. Tool 68 may include polymer source 86. The polymer for core 80 may be a thermoplastic that is melted to form a liquid polymer material or may be a polymer material that is dissolved in a solvent to form a liquid polymer material. Tool 68 may have a cavity and extrusion head (shown as portion 88) to receive polymer from source 86 and to hold the polymer in liquid form. Portion 88 of tool 68 may dispense the liquid polymer in the form of strand core 80. Strand core 80 may be formed using extrusion or other suitable techniques. If desired, spinning techniques may be used to produce spun strands. Other techniques may also be used in forming core 80. An optional pulley system or other equipment may be used to stretch core 80 to decrease the diameter of core 80. The core formation equipment of FIG. 4 is merely illustrative.

Following formation of polymer core 80, coating tool 62 may be used to apply coating 90 to core 80. Tool 62 may, as an example, apply a metal coating to core 80 using electrochemical deposition (e.g., electroless plating or electroplating using an applied current). Coating 90 may also be deposited by physical vapor deposition, chemical vapor deposition, dipping and curing (e.g., when coating core 90 with a conductive liquid layer coating layer such as a conductive polymer or a polymer with a conductive filler), application from a brush, needle, liquid-infused pad, or other dispenser, or other coating technique. After coating core 80 with conductive coating 90 to form coated strand 96, strand 96 may be wound onto drum 92 or provided directly to downstream processing equipment.

FIG. 5 is a diagram of illustrative equipment 66 for forming a polymer coating or other dielectric coating on the exterior of strand 96 (i.e., on coating 90 on strand core 80). As shown in FIG. 5, drum 92′ (which may be the same drum as drum 92 of FIG. 4 or another strand dispensing structure) may provide strand 96 (i.e., core 80 that has been coated with coating 90 using equipment of the type shown in FIG. 4) to coating equipment 100. Coating equipment 100 may include a source of liquid polymer precursor material such as liquid polymer reservoir 102. Liquid-impregnated pad 104 may be formed from a porous material such as open-cell foam, felt, or other material and may be used to apply liquid polymer coating 110 to the exterior of strand 96. If desired, liquid polymer materials may be dispensed by passing strand 96 through a pool of liquid polymer, by spraying, dripping, dipping, or other dispensing techniques. Curing equipment 112 may apply materials (e.g., catalyst) and/or energy (e.g., light such as ultraviolet light or heat) to coating 110, as indicated schematically by lines 114. Curing equipment 112 may, for example, be an oven or heat lamp for thermally curing liquid polymer precursor material to form an insulating polymer coating. Curing equipment 112 may also be based on a visible or ultraviolet light source, equipment for spraying or otherwise dispensing liquid catalyst, etc.

The curing of coating 110 to form a polymer insulating coating on the exterior surface of strand metal layer 90 forms conductive strand 22. Drum 120 or other equipment may be used to receive completed conductive strands such as strand 22. Strand 22 may then be provided with other strands (e.g., non-conductive strands 28) to strand intertwining equipment 70 to use in constructing item 10.

FIG. 6 is a cross-sectional side view of an illustrative strand core. Core 80 of FIG. 6 has a circular cross-sectional shape, but core 80 may have other shapes if desired. Core 80 may be formed from para-aramid fiber (e.g., Kevlar®), spun aromatic polyester fiber (e.g., Vectran®), or other polymer fiber. Core 80 is preferably thermally stable (e.g., core 80 is preferably able to withstand exposure to elevated temperatures without incurring damage). The elevated temperatures may be, for example, temperatures of 200-300° C., more than 150° C., more than 250° C., more than 350° C., less than 250° C., 210-220° C., or other suitable temperatures. Core 80 also preferably has a high elastic modulus (Young's modulus), such as a modulus of 50-250 GPa, 50-150 GPa, 100-200 GPa, more than 50 GPa, less than 250 GPa, etc. If desired, core 80 may have other advantageous physical attributes such as being insensitive to degradation due to exposure to light, having a good abrasion resistance, being highly flexible, exhibiting a high strength-to-weight ratio, forming a good electrical insulator, etc.

To form fabrics and other intertwined strands with desired properties, it may be desirable for the diameter of core 80 to be relatively small. As an example, diameter D of core 80 may be 50-70 microns, 25-100 microns, less than 100 microns, less than 150 microns, more than 10 microns, 10-200 microns, 10-500 microns, 150-250 microns, more than 50 microns, less than 400 microns, or other suitable diameter. The linear mass density of core 80 may be 220 denier, 130 denier, 55 denier, 28 denier, less than 100 denier, less than 75 denier, 75-20 denier, 75-25 denier, less than 60 denier, 60-25 denier, more than 10 denier, more than 20 denier, or other suitable linear mass density.

FIG. 7 is a cross-sectional side view of strand 96 (i.e., core 80 after coating with conductive coating layer 90). The thickness T1 of coating 90 may be 25 microns, more than 1 micron, more than 5 microns, less than 25 microns, less than 10 microns, less than 100 microns, 10-50 microns, 20-70 microns, more than 15 microns, more than 20 microns, less than 35 microns, less than 50 microns, less than 5 microns, or other suitable thickness. Coating 90 may be a metal (e.g., an elemental metal such as silver and/or a metal alloy) that has been deposited by electrochemical deposition, physical vapor deposition, etc. or may be any other suitable conductive layer.

FIG. 8 is a cross-sectional side view of conductive fiber 22. As shown in FIG. 8, conductive fiber 22 may have core 80, conductive coating 90, and insulating coating 110. Coating 110 may have a thickness T2 of 1-2 microns, more than 0.5 microns, less than 3 microns, less than 4 microns, 0.4-5 microns, less than 5 microns, less than 10 microns, less than 15 microns, less than 20 microns, 0.2-10 microns, more than 0.7 microns, or other suitable thickness. Coating 110 may include one or more dielectric sublayers (e.g., one layer, two layers, three layers, four layers, or more than four layers). To ensure that strand 22 can withstand elevated temperatures, coating 110 is preferably able to withstand elevated temperatures (e.g., temperatures of 200-300° C., more than 150° C., more than 250° C., more than 350° C., less than 250° C., 210-220° C., or other suitable temperatures). Examples of insulating coating materials that may be used for coating 110 include polyvinyl formal, polyester-polyimide, polyamide-polyimide, polyamide, polyimide, polyester, polytetrafluoroethylene, and polyurethane. Other polymers or mixtures of these polymers may be used, if desired. In configurations in which coating layer 110 is formed from multiple sublayers, each sublayer may be formed from the same material or some or all of the sublayers may be formed from different materials.

Illustrative steps involved in forming strands and items such as strands 12 and item 10 are shown in FIG. 9.

At step 200, a strand core for conductive strands such as strand 22 may be formed using equipment 68 (e.g., by extrusion of liquid polymer, by spinning of liquid polymer, etc.). The size of the strand core may, if desired, be relatively small (e.g., having a linear mass density of less than 100 denier) or may be any other suitable size.

At step 202, a metal coating or other conductive coating 90 may be formed using equipment 62 (e.g., electrochemical deposition equipment, physical vapor deposition equipment, etc.). The thickness of the metal coating may be relatively thin (e.g., less than 20 microns or other suitable thickness).

At step 204, dielectric coating equipment 66 may be used to form dielectric outer coating 110 on layer 90, thereby forming conductive strand 22. If desired, multiple strands may be braided together (e.g., 5-10 strands, more than 3 strands, fewer than 12 strands, etc.) to form a thread or other strand that contains multiple smaller strands. These smaller strands may be insulating and/or conductive strands. Insulating coating 110 may be formed by applying a liquid polymer coating to a relatively thin thickness and curing the applied coating using heat or light to produce cured coating 110 (e.g., a coating having a thickness of less than 5 microns or other suitable thickness).

At step 206, intertwining equipment 70 may be used to intertwine strands 12 and other equipment may be used in assembling strand-based materials into desired strand-based items such as item 10. To ensure that the physical properties of fabric and other items formed from intertwined strands 12 are satisfactory, it may be desirable to form conductive strands 22 with a size (e.g., diameter and/or denier) that is close (e.g., within 50%, within 25%, or within 10%) of the size (e.g., diameter and/or denier) of non-conducting strands 28. When these strands are woven, knitted, or otherwise combined to form fabric or other intertwined strand materials, the closeness of the size and other properties of strands 22 and 28 may help avoid undesired discontinuities in the appearance and feel of the fabric or other materials. Ensuring that the conductive and non-conductive strands in item 10 are similar in size may also help form electrical connections between overlapping strands (e.g., junctions such as junction 24 of FIG. 2 may be formed reliably).

In accordance with an embodiment. intertwined strands of material are provided that include non-conductive strands, and conductive strands that are intertwined with the non-conductive strands, each conductive strand has a strand core, a conductive coating on the strand core, and an insulating coating on the conductive core.

In accordance with another embodiment, the strand core of each conductive strand includes a dielectric material.

In accordance with another embodiment, the strand core of each conductive strand includes a polymer.

In accordance with another embodiment, the polymer is selected from the group consisting of polyamide, aromatic polyamide, polyimide, polyester, polyolefin, acrylic, aromatic polyesters, polyethylene, cellulosic polymer, and polyurethane.

In accordance with another embodiment, the polymer is a para-aramid.

In accordance with another embodiment, the polymer is an aromatic polyester.

In accordance with another embodiment, the conductive coating includes metal and the strand core has a linear mass density of less than 100 denier.

In accordance with another embodiment, the conductive coating includes silver.

In accordance with another embodiment, the insulating coating includes a polymer coating having a thickness of less than 5 microns.

In accordance with another embodiment, the insulating coating includes a polymer material selected from the group consisting of polyvinyl formal, polyester-polyimide, polyamide-polyimide, polyamide, polyimide, polyester, polytetrafluoroethylene, and polyurethane.

In accordance with another embodiment, the conductive coating is a metal coating.

In accordance with another embodiment, the strand core includes a material selected from the group consisting of para-aramid and polyester.

In accordance with another embodiment, the insulating coating has a thickness of less than 5 microns.

In accordance with another embodiment, the metal coating includes silver.

In accordance with another embodiment, the non-conductive strands have a first diameter, the conductive strands have a second diameter, and the second diameter is within 30% of the first diameter.

In accordance with another embodiment, the non-conductive strands have a first diameter, the conductive strands have a second diameter, and the second diameter is within 50% of the first diameter.

In accordance with another embodiment, the strand core of each conductive strand is a polymer strand, the conductive coating of each conductive strand is a metal coating, and the insulating coating of each conductive strand has a thickness of less than 3 microns.

In accordance with an embodiment, a fabric-based item is provided that includes circuitry, and intertwined strands of material including conductive strands that carry signals for the circuitry and non-conductive strands, the conductive strands each have a polymer strand core, a metal coating on the polymer strand core, and an insulating coating on the metal coating.

In accordance with another embodiment, the insulating coating has a thickness of less than 5 microns.

In accordance with another embodiment, the insulating coating includes a material selected from the group consisting of polyvinyl formal, polyester-polyimide, polyamide-polyimide, polyamide, polyimide, polyester, polytetrafluoroethylene, and polyurethane.

In accordance with another embodiment, the conductive coating includes metal and the strand core has a linear mass density of less than 100 denier.

In accordance with an embodiment, a fabric-based item is provided that includes electrical components that produce signals, and fabric that includes non-conductive strands and conductive strands, the conductive strands carry the signals and each conductive strand has a polymer strand core with a linear mass density of less than 100 denier, a metal coating on the polymer strand core, and an insulating coating with a thickness of less than 5 microns on the metal coating.

The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination. 

What is claimed is:
 1. Intertwined strands of material, comprising: non-conductive strands; and conductive strands that are intertwined with the non-conductive strands, wherein each conductive strand has a strand core, a conductive coating on the strand core, and an insulating coating on the conductive core.
 2. The intertwined strands of material defined in claim 1 wherein the strand core of each conductive strand comprises a dielectric material.
 3. The intertwined strands of material defined in claim 2 wherein the strand core of each conductive strand comprises a polymer.
 4. The intertwined strands of material defined in claim 3 wherein the polymer is selected from the group consisting of: polyamide, aromatic polyamide, polyimide, polyester, polyolefin, acrylic, aromatic polyesters, polyethylene, cellulosic polymer, and polyurethane.
 5. The intertwined strands of material defined in claim 3 wherein the polymer is a para-aramid.
 6. The intertwined strands of material defined in claim 3 wherein the polymer is an aromatic polyester.
 7. The intertwined strands of material defined in claim 1 wherein the conductive coating comprises metal and wherein the strand core has a linear mass density of less than 100 denier.
 8. The intertwined strands of material defined in claim 7 wherein the conductive coating comprises silver.
 9. The intertwined strands of material defined in claim 8 wherein the insulating coating comprises a polymer coating having a thickness of less than 5 microns.
 10. The intertwined strands of material defined in claim 1 wherein the insulating coating comprises a polymer material selected from the group consisting of: polyvinyl formal, polyester-polyimide, polyamide-polyimide, polyamide, polyimide, polyester, polytetrafluoroethylene, and polyurethane.
 11. The intertwined strands of material defined in claim 10 wherein the conductive coating is a metal coating.
 12. The intertwined strands of material defined in claim 11 wherein the strand core comprises a material selected from the group consisting of: para-aramid and polyester.
 13. The intertwined strands of material defined in claim 12 wherein the insulating coating has a thickness of less than 5 microns.
 14. The intertwined strands of material defined in claim 13 wherein the metal coating comprises silver.
 15. The intertwined strands of material defined in claim 14 wherein the non-conductive strands have a first diameter, wherein the conductive strands have a second diameter, and wherein the second diameter is within 30% of the first diameter.
 16. The intertwined strands of material defined in claim 1 wherein the non-conductive strands have a first diameter, wherein the conductive strands have a second diameter, and wherein the second diameter is within 50% of the first diameter.
 17. The intertwined strands of material defined in claim 16 wherein the strand core of each conductive strand is a polymer strand, wherein the conductive coating of each conductive strand is a metal coating, and wherein the insulating coating of each conductive strand has a thickness of less than 3 microns.
 18. A fabric-based item, comprising: circuitry; and intertwined strands of material including conductive strands that carry signals for the circuitry and non-conductive strands, wherein the conductive strands each have a polymer strand core, a metal coating on the polymer strand core, and an insulating coating on the metal coating.
 19. The fabric-based item defined in claim 18 wherein the insulating coating has a thickness of less than 5 microns.
 20. The fabric-based item defined in claim 19 wherein the insulating coating comprises a material selected from the group consisting of: polyvinyl formal, polyester-polyimide, polyamide-polyimide, polyamide, polyimide, polyester, polytetrafluoroethylene, and polyurethane.
 21. The fabric-based item defined in claim 20 wherein the conductive coating comprises metal and wherein the strand core has a linear mass density of less than 100 denier.
 22. A fabric-based item, comprising: electrical components that produce signals; and fabric that includes non-conductive strands and conductive strands, wherein the conductive strands carry the signals and wherein each conductive strand has a polymer strand core with a linear mass density of less than 100 denier, a metal coating on the polymer strand core, and an insulating coating with a thickness of less than 5 microns on the metal coating. 